Small note for everyone planing to use Linux LVM snapshots and using XFS at the same time. XFS has UUIDs which are unique identifiers of the filesystem. Two file systems with same UUID can not be mounted on the same server. Now, if we know that a snapshot of a logical volume represents a point-in-time copy of the original logical volume it doesn't take much time to realize that the filesystem on the snapshot is also a copy, thus it will have the same UUID as the filesystem on the original logical volume. So here is what happens when you try to mount the snapshot:

XFS was a default choice for many years in the company when I arrived here. Some of the reasons are very good handling of big files (important for DB servers for example), fast recovery and possibility of online resize (ext3 was not able to do this at the time).

But there are some downsides as well. For example XFS is very prone to fragmentation so from time time defragmentation is necessary (although this can be done online). Also it is not a “standard” filesystem, so many backup solutions do not work with XFS (although they support reiserfs, blah!). We are having a big problem finding good online system backup solution for our servers. I would be grateful for recommendations! :-)